1. Field of the Invention
The invention relates to a display for showing text and graphic images with an electrically conducting layer. Displays with an electrically conducting layer. Displays with an electrically conducting layer are known in the prior art and are used to make the display form a so-called “touch screen” or, for example in the case of liquid-crystal displays, to heat them. Heating devices are used in the case of liquid-crystal displays in order that they can operate quickly even at low temperatures, as may occur for example when they are used in motor vehicles, and in this way prevent a display with a slow response.
2. Description of the Prior Art
A “touch screen” is known in the prior art and is used to allow menus, submenus, values or icons represented on a screen to be selected by touching the respective representation with a finger or some other input means. In the case of an analog resistive touch screen, a plate of toughened glass with an electrically conductive coating with a uniform electrical resistance is arranged in front of the display. A sheet of polyester is stretched over this glass upper side and separated from it by small, transparent insulating points. The variable sheet has a hard, durable coating on the outer side and a conductive and highly transparent indium-tin-oxide coating on the inside. Even when touched lightly, the conductive coating establishes an electrical connection with the coating on the glass. By means of an integrated controller, a voltage gradient is set up on the conductive coating. The voltages at the contact point form an image of the touched position with the aid of analog values. The controller digitizes these voltages and sends them to a processing device to determine the touched positions.
A capacitive touch screen comprises a clear plate which has been coated with a resistively capacitive material and an insulating material. An electromagnetic field is generated over the plate. If a conducting object, for example a finger or metal rod, touches the screen and grounds it, the electromagnetic field changes. The place which was touched can be concluded from the change in the electromagnetic field.
Displays and the driver circuits controlling them are operated with high frequencies. Consequently, undesired electromagnetic disturbances can occur in the area surrounding the displays. If a display is used in an instrument cluster of a motor vehicle, the radio reception and/or the cell phone reception in the motor vehicle for example may be disturbed.